Their paid managed service works well for enterprise SaaS companies who need < 3-4 TB of storage max ever per customer cluster and have enterprise scale users (<100k users).

It also works well for early stage Consumer Internet startups that haven't yet achieved huge growth but care a lot about developer productivity while churning features at high velocity.

But it gets blamed for reliability issues suffered by highly successful Consumer Internet companies that have achieved scale and have DAU, MAU in > 10M and have lot more than 4TB of data in a single cluster.

But that's basically a good problem to have at that stage. Usually such a company would have many more problems – monolithic application with monolithic database with huge unmanageable schema and indexes gone wild etc. Usual solution at that stage would be some sort of rearchitecture towards Microservices with multiple specialized databases for different use-cases – usually cloud hosted managed databases with horizontal scalability dedicated for online user-path workloads and separate OLAP tech stack for offline ETL/analytics workloads.